Biomedical subjects

A C Pollard

Publications and source records attributed to A C Pollard.

At least 55 records · Page 3Linked to original sources

PubMed1977

A rapid and sensitive gas-liquid chromatographic procedure for the micro determination of sodium valproate (sodium di-N-propylacetate) in plasma or serum.

A gas-liquid chromatographic procedure for the micro determination of sodium valproate is described. Valproic acid is extracted from acidified plasma or serum into n-heptane containing an internal standard (octanoic acid) and after phase separation an aliquot is analysed by gas-liquid chromatography. The procedure is rapid, reliable, sensitive and specific. It requires 25--50 microliter sample for a single estimation, has a detection threshold of less than 10 mumol/l, and is suitable for routine clinical use.

Chromatography, Gas↗

PubMed1977

A micro-radiochemical assay for alpha-1,4-glucosidase and its use in the assessment of type II glycogenosis (Pompe's disease).

An assay for alpha-1,4-glucosidase (acid maltase) activity which is deficient in Pompe's disease is described. The assay can be used to measure the enzyme in cultured skin fibroblasts, cultured amniotic cells and peripheral blood leucocytes. [U-14 C]Maltose is used as the substrate in a total assay volume of 8 microliter. The product, [U-14C]glucose, is separated from the substrate by cellulose thin-layer chromatography. The procedure permits replicate assays from 400 microliter whole blood and from amniotic cells in primary culture. Discrimination of the heterozygous Pompe state appears to be facilitated.

Amnion↗

PubMed1977

Variability of fibroblast lysosomal acid hydrolases with reference to the detection of enzyme deficiencies.

The ranges of variability of eight lysosomal acid hydrolases were examined in 47 cultured human skin fibroblast lines through 5 successive subcultures. No overall trend in activity values was found for any of the enzymes tested between the first and final subcultures. Similarly, no significant differences could be found between the overall ranges of fibroblast enzyme activity between 20 clinically normal children and 27 individuals being investigated for non-specific metabolic diseases. It is concluded that for diagnostic reference purposes, wide ranges of normal enzyme values must be established. Such ranges can be validly drawn from a continuation of both clinical groups irrespective of the passage number (up to 5) of the cells at the time of isolation. It is noted that in certain cell lines derived from Fabry and Gaucher patients the 'residual' activity of the expectedly deficient enzyme could not easily be distinguished from the lowest values observed in normals, whereas, as expected, the activity of cells derived from patients with GM1 and GM2 gangliosidoses was markedly reduced.

Adult↗

PubMed1977

Considerations in the prenatal assessment of lysosomal enzyme deficiency in eight cases at risk.

Some of the factors which are to be considered in the antenatal diagnostic evaluation of lysosomal enzyme levels in cultured amniotic fluid cells are discussed in the light of eight consecutive cases in which the foetuses had a 1 in 4 chance of being homozygous for a lysosomal storage disease. There were 2 possible cases of GM1 gangliosidosis, 2 of neuropathic Gaucher's disease, 1 of Krabbe's disease and 2 of Pompe's disease. Each infant was predicted to be unaffected; the assessments were confirmed to be correct postnatally--7 by enzyme studies. Using a micro technique, 5 of the assessments were available in 28 days or less following amniocentesis. It is concluded that in certain circumstances skin fibroblasts may be used as valid controls and that the variability of assay results strongly militates against the confident assignment of heterozygous status and may cause difficulties in the identification of the homozygote in cases where 'residual' enzyme activity is high; concomitant family studies assist in the resolution of such problems.

Amniotic Fluid↗

PubMed1976

A potential source of error in the enzymatic diagnosis of the neurolipidoses when radiolabelled sphinogolipids are used as substrates.

High specific activity 3H-labelled glucocerebroside, galactocerebroside and sphingomyelin but not 3H-labelled ceramide, have been found to bind to the wall of glass scintillation vials thereby greatly decreasing the counting efficiency. The binding of the lipids was largely eliminated by counting samples in scintillation fluid containing methanol (6-10%, v/v). To avoid possible errors in the enzymatic diagnosis of the neurolipidoses, it is suggested that the latter solvent should be routinely incorporated into scintillation fluid used for counting labelled sphingolipids.

Ceramides↗

PubMed1976

A transient variant of serum lactate dehydrogenase isoenzymes.

An unusual variant of the serum lactate dehydrogenase (LDH) isoenzyme pattern is described in an apparently healthy young woman. The abnormal pattern consisted of a single zone of LDH activity, having the same mobility as, but more diffuse than, normal LDH-4. The molecular weight of the abnormal LDH complex is approximately 280 000, but the nature of the additional component remains unknown, as the isoenzyme pattern spontaneously reverted to normal six weeks after it was first noticed.

Adult↗

PubMed1976

A rapid method for the estimation of beta-galactocerebrosidase, beta-glucocerebrosidase and sphingomyelinase activities in leukocytes.

A method for the assay of leukocyte beta-galactocerebrosidase, beta-glucocerebrosidase and sphingomyelinase activities has been developed, based on the separation of the tritiated sphingolipid substrates from their corresponding radioactive hydrophobic product (ceramide) by thin-layer chromatography on Silica gel H coated microscope slides. For the determination of beta-galactocerebrosidase and beta-glucocerebrosidase activities the silica gel is impregnanted with sodium tetraborate. Each chromatogram is easily divided into two distinct zones and the radioactivity content of each is determined by liquid scintillation counting. The technique described, is rapid, less costly than conventional methods and provides an accurate assessment of sphingolipid hydrolase activity. It is suggested that it should be of considerable value in those areas which require the rapid analysis of large numbers of samples, such as in screening for the sphingolipidoses or for enzyme purification studies.

Chromatography, Gas↗

PubMed1976

A rapid and sensitive spectrophotometric procedure for the micro determination of carbamazepine in blood.

An ultraviolet spectrophotometric procedure for the micro determination of carbamazepine in blood is described which is based on the original 9-methyl-acridine method proposed by Beyer, K.H. and Klinge, K. (1969) (Arzneim-Forsch. 19, 1759--1760). Carbamazepine is extracted from blood with dichloromethane, which is then washed with alkali and acid. An aliquot of the extractant is evaporated to dryness and the residue heated briefly with hydrochloric acid at 150 degrees C. Following removal of non-specific interference with n-heptane, the absorbance of the acid catalysed rearrangement product (9-methylacridine) is determined at 258 nm. The resulting procedure is rapid, reliable, sensitive and specific. It requires 100-200 mul sample for a single estimation and has a detection threshold of less than 0.1 mg/100 ml. It is concluded that the method is suitable for routine clinical use.

Acridines↗

PubMed1976

A rapid spectrophotometric procedure for the simultaneous micro determination of carbamazepine and 5, 5-diphenyl-hydantoin in blood.

Carbamazepine and 5,5-diphenylhydantoin are simultaneously extracted from 100-200 mul blood with 1,2-dichloroethane. 5,5-Diphenylhydantoin is removed by a one-step wash into alkali. The dichloroethane is further washed with acid and then evaporated to dryness. 5,5-Diphenylhydantoin is determined in the alkali washing by a benzophenone procedure; carbamazepine is determined in the dried residue by the 9-methylacridine procedure earlier described. The combined method is rapid, reliable and has a detection threshold of less than 0.1 mg/100 ml for each drug.

Acridines↗

PubMed1976

Management of phenylketonuria: South Australian experience of 13 cases.

The management and present status of 13 children with phenylketonuria detected on the fifth day of life, who have been treated by diet thereafter for five to eight years, are discussed. In all 10 cases in which there has been continuous adequate dietary control of blood phenylalanine levels, the physical, social and mental development of the children has been normal. In some of these cases there is an unexplained discrepancy between the verbal and performance IQ scores. The present policy is to continue restricting the diet indefinitely, relaxation being permitted conditionally only after the age of seven years.

Australia↗

PubMed1975

Bioavailability of phenytoin from various pharmaceutical preparations in children.

In children, the blood level of phenytoin was found to be significantly higher when 100 mg capsules rather than 100 mg tablets were administered. When, on the other hand, 30 mg capsules and tablets were compared; the situation was reversed; tablets produced significantly higher blood levels of phenytoin than did the capsules. The significance and possible explantation of these findings are discussed.

Adolescent↗

PubMed1975

An improved benzophenone procedure for the micro-determination of 5,5-diphenylhydantoin in blood.

A micro-modification of the benzophenone procedure proposed by Wallace for the determination of 5,5-diphenylhydantoin in blood is described which does not require specialised glassware and avoids the interferance caused by chloroform. In the new procedure 5,5-diphenylhydantoin is extracted from blood with 1,2-dichloroethane, returned to alkali, washed with n-heptane, and oxidised with permanganate in small teflon lined screw capped test tubes containing a layer of n-heptane. The absorbance of the oxidation product (benzophenone) is measured spectrophotometrically on an expanded scale using semi micro cuvettes. The method requires 100-200 mul sample and has a detection threshold of less than 0.1 mg/100 ml.

Benzophenones↗

PubMed1975

Diagnostic significance and source of lactate dehydrogenase and its isoenzymes in cerebrospinal fluid of children with a variety of neurological disorders.

Two hundred and thirty-four cerebrospinal fluid (CSF) specimens from 183 different children were analysed for total lactate dehydrogenase (LD) activity and LD isoenzyme distribution. The LD activities were elevated in the CSF of patients with meningitis, especially with bacterial infections, and with central nervous system (CNS) leukaemia. The CSF LD isoenzyme patterns of both groups generally reflected the number and distribution of lymphocytes and granulocytes in the CSF. Increases in CSF LD levels also occurred in patients with other neurological disorders, such as hydrocephalus, raised intracranial pressure, and epileptic seizures. However, no significant increases in CSF LD activity nor abnormality of the isoenzyme distribution were noted in children who had had a non-specific febrile convulsion.

Bacterial Infections↗

PubMed1973